DOYLESTOWN, Pa. — A Pennsylvania man has admitted to killing four of his acquaintances, after bodies were found buried on his parents’ farm in Bucks County, the man’s lawyer said on Thursday.

Cosmo DiNardo, 20, had been described by prosecutors as a “person of interest” in the disappearance of the other young men, and investigators searching the sprawling farm in a suburb of Philadelphia found human remains in a deep grave there.

One set of remains has been identified as one of the missing men, and the others are still being identified.

“Mr. DiNardo this evening confessed to the district attorney to his participation or commission in the murders of the four young men,” one of his lawyers, Paul Lang, told reporters late Thursday outside the Bucks County Court of Common Pleas. “In exchange for that confession, Mr. DiNardo was promised by the district attorney that he will spare his life by not invoking the death penalty.”

District Attorney Matthew D. Weintraub had no immediate comment, but scheduled a news conference for later in the evening.

The announcement came after the authorities charged Mr. DiNardo with stealing one of the men’s cars and trying to sell it for $500. Mr. DiNardo came under scrutiny early in the investigation.

The first set of remains was discovered in a 12.5-foot-deep “common grave” on the Bucks County farm, where local authorities, as well as an evidence response team from the Philadelphia office of the F.B.I., had brought in cadaver dogs, sifted through soil in rows of corn, dug up concrete with a backhoe and surveyed the land on all-terrain vehicles.

Cadaver dogs led detectives to the grave, Mr. Weintraub said at a news conference early on Thursday. He said the body of Dean Finocchiaro, 19, who vanished around 6:30 p.m. Friday in Middletown Township, had been identified.

The first to disappear, Jimi Tar Patrick, 19, was last seen around 6 p.m. on July 5 in Newtown Township, Pa., and did not show up for work the next day, the authorities said.

Last Friday around 6 p.m., Mark Sturgis, 22, told his father that he was going to meet up with his longtime best friend, Tom Meo, 21, and that they would be ready for their construction jobs the next morning. They did not show up, and their cellphones went straight to voice mail.

The authorities in Bucks County, a fast-growing suburb with rolling hills and vast estates, have called the painstaking search among the largest law enforcement efforts in the county’s history.